Thin sanitary paper roll method of manufacturing the paper roll, and thin sanitary paper for thin sanitary paper roll

ABSTRACT

Disclosed is a sanitary tissue paper roll wherein, when a sanitary tissue paper roll of two-ply or three-ply is laid on a horizontal surface with its central axis in a horizontal orientation, and a circular plate indenter, having an area of 2 cm 2  and being arranged at a center of an upper surface of an outer periphery of a body of the roll, is vertically pressed at least at respective pressing pressures of 0.5 gf/cm 2  and 50 gf/cm 2 , a difference in depths upon this respective pressing is within a range of 2.5–3.5 mm. Also disclosed is a sanitary tissue paper roll made by winding one sheet or two layered sheets of sanitary tissue papers wherein a roll compressibility of the roll is 0.68–0.74 m/cm 2 , with the roll compressibility being defined as a value obtained by dividing a roll length by a cross section of the roll. Also disclosed is a sanitary tissue paper for a sanitary tissue paper roll, wherein a sample paper is compressed between steel plates, which respectively have a circular surface with a compression area of 2 cm 2 , at a maximum compression load of 50 gf/cm 2 , and upon returning of this paper sample, a linearity of a displacement curve between a load and a thickness is 0.2500–0.3300 for a one-ply, and 0.3400–0.3700 for a two-ply; and a thickness upon a load of 50 gf/cm 2  is equal to at least 0.1400 mm for a one-ply, and equal to at least 0.2500 mm for a two-ply.

TECHNICAL FIELD

The present invention relates to a sanitary tissue paper roll such as atoilet paper roll, a method of making the same, and a sanitary tissuepaper for a sanitary tissue paper roll.

BACKGROUND ART

Toilet paper rolls (also called toilet rolls), as sanitary tissue paperrolls, are generally made by winding one sheet to three layers of sheetsof sanitary tissue papers onto a paper core and into a roll (thoughthere are products without paper cores). Usually, a roll made by windingone sheet of sanitary tissue paper is called one-ply, a roll made bywinding two-layered sheets of sanitary tissue papers is called atwo-ply, and a roll made by winding three-layered sheets of sanitarytissue papers is called a three-ply.

Particularly, in a case of toilet paper rolls made of 100% natural pulp,embossing is applied to the sanitary tissue paper to provide a thicknessfeeling and bulk softness. In a toilet paper roll made of such pulp,usually, about 60 m of sanitary tissue paper for one-ply, and about 30 mfor two-ply, is wound onto a paper core having an inner diameter of 45mm and a thickness of 0.5 mm, and made into a roll having about an 110mm outer diameter. Recently, there are rolls called compact rolls inwhich 90 m for one-ply and 45 m for two-ply is wound around a paper corehaving an outer diameter of about 38 mm.

In such toilet paper rolls, since the toilet paper comes directly intocontact with sensitive skin, rigorousness in quality is required from aconsumer. That is, these products are always exposed to a consumer'srigorous selection, and thus, there are several high hurdles to beovercome in order for these products to be used.

A first hurdle is to provide a good image upon purchasing so that theproduct will be tried once. A second hurdle is not to disappoint theabove-mentioned image, i.e., a consumer's expectations, upon actualusage.

(A) Object of Toilet Paper Roll in Order to Overcome the First Hurdle

Toilet paper rolls are usually displayed and sold in stores in packageswherein a plurality of toilet paper rolls are packed. It is thought thata consumer decides whether or not to purchase the rolls by holding thetoilet paper roll in his/her hand, and by unconsciously imagining afeeling of the toilet paper upon use, based on the feeling upon holding.

Through this fact, the present applicant found that the feeling uponholding the toilet paper roll, that is, hardness felt upon holding theroll, becomes a potential purchasing index for deciding whether or notto purchase the roll. It is thought that purchasing is decided based onthe thought that, for example, if the toilet paper roll feels hard uponholding the roll, the paper may be hard and uncomfortable upon usage inthe form of a sheet in an unwound actual usage state, or, if the roll istoo soft, the paper may rip upon usage because it is too soft also inthe form of a sheet.

However, roll hardness of toilet paper rolls currently put on the marketdoes not possess a suitable tender-touch. Thus, it is inferred thatthere are many cases where the rolls are losing an opportunity of beingtried.

(B) Object Upon Giving the Toilet Paper Roll a Suitable Roll Hardness

On the other hand, in order to provide the roll hardness with a suitabletender-touch, there are the following objects. That is, conventionalsanitary tissue paper rolls were either wound too hard and had poorthickness feeling or bulk softness, or on the contrary, wound too looseand the rolls easily deformed in a telescopic manner in which a centralportion projects from sides, or their section deformed into a polygonalshape, and was poor in massiveness when holding in a hand.

Particularly, in a case where the roll was wound hard, although it isthought that by applying the above-mentioned embossing, the thicknessfeeling and bulk softness can be improved, only by providing clearembosses, an emboss is stretched and flattened and the thickness feelingand bulk softness are lost upon winding or as time passes due to tensionin a winding direction. Further, in case of forming a compact roll,since sanitary tissue paper is wound around a core while beingtensioned, an emboss is stretched and flattened due to this tension.Thus, it is not possible to enhance a thickness feeling and bulksoftness.

On the other hand, if the paper is softly wound merely by loweringtension upon winding, windings tend to easily loosen. This not onlybecomes a cause of defectively wound items and deteriorates massiveness,but also causes a problem in that a roll diameter becomes too large eventhough a roll length is short. Particularly, if winding is performedwith a usual roll length after providing clear embosses to increasepaper thickness, even though flattening of the embosses can beprevented, the roll diameter becomes too large and the rolls cannot beheld by usual holders.

(C) Object of Sanitary Tissue Paper for Toilet Paper Roll in Order toOvercome the Second Hurdle

Upon unwinding and actually using the toilet paper roll having beenpurchased mainly by image as explained above, it is necessary not togive an impression to a consumer, who purchased the roll, that he hasbeen betrayed of his/her expectations. Further, upon use, the consumerwill sensually evaluate, for example, a tender-touch, pliantness, bulksoftness, hardness, and smoothness of the roll in a state of a sanitarytissue paper having been unwound from the toilet paper roll.

Therefore, conventionally, in addition to paper-quality data such asgrammage, paper thickness, strength, and elongation which aregenerally-measured physical properties of paper, it has been typical fora manufacturer to adopt indexes such as “softness” or “MMD” asevaluation criteria corresponding to such sensory evaluation.

“Softness” shows a resistance value (average value in longitudinal andlateral directions) when pushing a paper, being 10 cm wide, into a 5.0mm gap using a terminal. “MMD” shows a variation (average deviation) ina friction coefficient between paper and a contactor wound with a pianowire. These are measuring methods used generally for sanitary papers.

However, “softness” is affected by friction between the paper and theterminal, and does not always sufficiently correspond to tender-touchand/or pliantness evaluated by a person. Further, although “MMD” has arelationship with smoothness felt by skin, this resulting value has notbeen able to show a difference between a mere slippery feeling andsmoothness.

Therefore, it has not been able to sufficiently grasp bulk softness,pliantness, tender-touch and/or smoothness to the touch, which arerequired for toilet papers, and thus, it was not possible to reproducequality nor confirm that quality has been reproduced.

Only by paper-quality data, softness and MMD, a delicate quality felt bya person was not sufficiently grasped, nor was it possible tosufficiently conduct an absolute evaluation in a time series or adifferential analysis compared with competitive products made by othercompanies.

SUMMARY OF THE INVENTION

In view of the above and other matters, one aspect of a sanitary tissuepaper roll of the present invention is, for example, such wherein, whena sanitary tissue paper roll of two-ply or three-ply is laid on ahorizontal surface with its central axis in a horizontal orientation,and a circular plate indenter, having an area of 2 cm² and beingarranged at a center of an upper surface of an outer periphery of a bodyof the roll, is vertically pressed at least at respective pressingpressures of 0.5 gf/cm² and 50 gf/cm², a difference in depths upon thisrespective pressing is within a range of 2.5–3.5 mm.

Another aspect of the sanitary tissue paper roll of the presentinvention is, for example, such wherein, when a sanitary tissue paperroll of one-ply is laid on a horizontal surface with its central axis ina horizontal orientation, and a circular plate indenter, having an areaof 2 cm² and being arranged at a center of an upper surface of an outerperiphery of a body of the roll, is vertically pressed at least atrespective pressing pressures of 0.5 gf/cm² and 50 gf/cm², a differencein depths upon this respective pressing is within a range of 1.5–2.5 mm.

Note that various other aspects may be contrived regarding the presentinvention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing a method of measuring roll hardnessof a toilet paper roll according to the present invention;

FIG. 2 is a diagram of a correlation between a difference in pressingdepth and a sensory-evaluation value for a toilet paper roll having aninner/outer roll diameter of 40 mm/110 mm;

FIG. 3 is a graph showing measurement results upon continuouslymeasuring the above-mentioned difference in pressing depth nine timesfor the above-mentioned two-ply toilet paper roll having an inner/outerroll diameter of 40 mm/110 mm;

FIG. 4( a) is a side sectional view of a sheet with a small elongationrate, and FIG. 4( b) is a side sectional view of a sheet with a largeelongation rate;

FIGS. 5( a)–5(b) are side views of a toilet paper roll;

FIG. 6 is a schematic perspective view of an example of a cored-toiletpaper roll;

FIG. 7 is an explanation diagram of a compression-characteristic testingmethod of the present invention;

FIG. 8 is an explanation diagram of a bending-characteristic testingmethod of the present invention;

FIG. 9 is a relational diagram regarding bending characteristics; and

FIG. 10 is an explanation diagram of a frictional-characteristic testingmethod of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention was construed to solve the above and otherproblems, and a first object is to provide a sanitary tissue paper rollwhich can give an appropriate tender-touch feeling when a consumer takesthe roll in his/her hand.

A second object is to provide a sanitary tissue paper roll which is richin thickness feeling and bulk softness while being difficult to deform,which has a sufficient massiveness when taken in the hand, and in whichan emboss is not easily flattened in case embossing is applied.

Further, a third object is to provide a sanitary tissue paper for asanitary tissue paper roll which is superior and matches human sensoryevaluation, and which is highly valued in terms of such sensoryevaluation. Other objects are to permit quantification of bulk softness,pliantness and smoothness of a sanitary tissue paper, and to permitmanagement and control of quality of this toilet paper according tomeasurement data, by using a combination of two measurement data forrespective three basic measurement methods, or by using the three basicmeasurement methods and six measurement data.

In order to achieve the above and other objects, the sanitary tissuepaper roll according to one aspect of the present invention is suchwherein, when a sanitary tissue paper roll of two-ply or three-ply islaid on a horizontal surface with its central axis in a horizontalorientation; and a circular plate indenter, having an area of 2 cm² andbeing arranged at a center of an upper surface of an outer periphery ofa body of the roll, is vertically pressed at least at respectivepressing pressures of 0.5 gf/cm² and 50 gf/cm², a difference in depthsupon this respective pressing is within a range of 2.5–3.5 mm.

According to the structure above, when a consumer takes a two-ply orthree-ply sanitary tissue paper roll in his/her hand, the consumer canfeel an appropriate tender-touch. This is because a difference inpressing depth of the present sanitary tissue paper roll is set withinan appropriate range of 2.5–3.5 mm based on a correlation between asensory-evaluation value of roll hardness, which is felt by a persontaking the sanitary tissue paper roll in his/her hand, and theabove-mentioned difference in pressing depth, in order to provide anappropriate soft feeling to a person holding the roll. That is, sincethe difference in pressing depth is set to be equal to at least 2.5 mm,the consumer is not given a feeling that the roll is too hard; whereas,since the above-mentioned difference in pressing depth is set equal toat least 3.5 mm, he is not given a feeling that the roll is too soft.Therefore, the consumer can feel an appropriate tender-touch.

Further, it is possible to objectively and quantitatively evaluate asensory-evaluation value, which expresses roll hardness felt by aperson, as a difference in pressing depth upon pressing a circular plateindenter into the roll at two pressing pressures. Therefore, it ispossible to control the roll hardness of a sanitary tissue paper rollwithin an appropriate range.

A sanitary tissue paper roll according to one aspect of the presentinvention is such wherein, when a sanitary tissue paper roll of one-plyis laid on a horizontal surface with its central axis in a horizontalorientation, and a circular plate indenter, having an area of 2 cm² andbeing arranged at a center of an upper surface of an outer periphery ofa body of the roll, is vertically pressed at least at respectivepressing pressures of 0.5 gf/cm² and 50 gf/cm², a difference in depthsupon this respective pressing is within a range of 1.5–2.5 mm.

According to the structure above, it is possible to achieve the sameeffects, like the above-mentioned invention, for a one-ply sanitarytissue paper roll.

A sanitary tissue paper roll according to one aspect of the presentinvention is such wherein, when a sanitary tissue paper roll of one-plyto three-ply is laid on a horizontal surface with its central axis in ahorizontal orientation, a circular plate indenter, having an area of 2cm² and being arranged at a center of an upper surface of an outerperiphery of a body of the roll, is vertically pressed at least atrespective pressing pressures of 0.5 gf/cm² and 50 gf/cm², and adifference in depths upon this respective pressing is continuouslymeasured nine times, a difference between a maximum and a minimum of allvalues of these measurements is within a range of 0.5–1.0 mm.

According to the structure above, since the above-mentioned differencebetween the maximum and minimum of the measurement values is within arange of 0.5–1.0 mm, an appropriate restorability and ability to deformpermanently will be provided. Thus, the sanitary tissue paper roll willbe able to possess both an appropriate shape-maintaining ability andtender-touch. To the contrary, if the difference exceeds 1.0 mm, theroll is easily subjected to permanent deformation and ashape-maintaining ability is deteriorated; whereas if the difference isbelow 0.5 mm, permanent deformation is difficult to occur and the rollwill feel hard.

Therefore, according to the above, it is possible to provide a consumerwith an appropriate tender-touch feel when the consumer takes theabove-mentioned sanitary tissue paper roll in his/her hand, and the rollwill appropriately maintain its roll shape and be superior in appearancedue to its appropriate shape-maintaining ability.

In a sanitary tissue paper roll according to one aspect of theabove-mentioned present invention, it is possible that, when adifference in depths upon respective pressing is continuously measurednine times, all values of these measurements are within a range of adifference in pressing depth; and a difference between a maximum and aminimum of all values of these measurements is within a range of 0.5–1.0mm.

Further, in a sanitary tissue paper roll according to one aspect of theabove-mentioned present invention, it is possible that an elongationrate in a longitudinal direction of sanitary tissue paper of thesanitary tissue paper roll is 20–35%.

According to the structure above, since a sanitary tissue paper havingan elongation rate, in the longitudinal direction, of 20–35% is used forthe sanitary tissue paper roll, it is possible to easily set adifference in pressing depth in a rolled state within an appropriaterange (range of 2.5–3.5 mm for two-ply or three-ply, and range of1.5–2.5 mm for one-ply), as well as provide a shape-maintaining abilityto the roll.

For example, in case a sheet having an elongation rate below 20% isused, when the sheet is wound into a roll with a constant windingtension, since crepes (wrinkles along a width direction of the sheet, aplurality of which are provided in the longitudinal direction) are fullystretched and no elongation remains, there are cases where bulkinessbecomes small and the roll becomes hard. On the other hand, if the sheetis wound with a low roll compressibility to maintain elongation in orderto avoid the above-mentioned situation, since the crepes are small, aspace tends to be created between the sheets and winding becomes loose,resulting in that the roll is easily deformed by, for example, a lateralprotrusion of a side-end surface of the roll in a telescopic manner.That is, it is difficult to cope with both setting the above-mentioneddifference in pressing depth, which expresses roll hardness, within theabove-mentioned appropriate range, and maintaining the shape of theroll.

Further, in case a sheet having an elongation rate exceeding 35% isused, crepes remain too large when the sheet is wound into a roll,resulting in that bulkiness becomes too large and the roll becomesexcessively soft. Therefore, it is difficult to set the above-mentioneddifference in pressing depth within the above-mentioned appropriaterange.

Contrary to the above, if a sheet having an elongation rate of 20–35% isused, since crepes remain to have an appropriate size even when thesheet is wound into a roll, bulkiness can be set to an appropriateextent, and a difference in pressing depth can easily be set within theabove-mentioned appropriate range. Further, since sheets, which arestacked in a radial direction, are resiliently bound together because ofthe crepes remaining in an appropriate size, side-end surfaces will noteasily protrude laterally in a telescopic manner, and aroll-shape-maintaining ability is superior. That is, it is possible toachieve both setting the above-mentioned difference in pressing depthwithin the appropriate range, and maintenance of the shape of the roll.

The invention of a sanitary tissue paper roll according to anotheraspect of the present invention is made by winding one sheet or twolayered sheets of sanitary tissue papers wherein a roll compressibilityof the roll is 0.68–0.74 m/cm², with the roll compressibility beingdefined as a value obtained by dividing a roll length by a cross sectionof the roll.

According to the structure above, when the roll compressibility iswithin a range of 0.68–0.74 m/cm², the roll will be rich in terms of athickness feeling and bulk softness while being difficult to deform, andembosses will not easily be flattened in case embossing is applied. Tothe contrary, if the roll compressibility exceeds 0.74 m/cm², windingwill be too hard and a thickness feeling and bulk softness willdecrease. Then, if the roll compressibility is below 0.68 m/cm²,deformation will easily occur and massiveness when held will decrease.

Further, a sanitary tissue paper roll according to one aspect of theabove-mentioned present invention is such that a dry-state tensilestrength, which is measured according to a tensile-characteristictesting method defined by JISP8113, per each sheet of sanitary tissuepaper is equal to at least 40 N/m in a width direction, and is 1.0–4.0folds of the width direction in a longitudinal direction.

According to the structure above, by heightening a width-directiondry-state tensile strength to a necessary-and-sufficient extent and alsosetting a longitudinal-direction dry-state tensile strength to 1.0–4.0folds of the width-direction dry-state tensile strength, the sanitarytissue paper will not easily be tightened into a hard, thin state uponwinding or after winding, and thus, a thickness feeling, bulk softnessand massiveness upon usage are sufficiently secured, even if the rollcompressibility is set to be 0.68–0.74 m/cm². Particularly, in caseembossing is applied to the sanitary tissue paper, this emboss is noteasily flattened and will clearly remain upon usage, and a thicknessfeeling, bulk softness and massiveness will not easily be lost.

Further, a sanitary tissue paper roll according to one aspect of theabove-mentioned present invention is such that a number of crepes ofsanitary tissue paper is 25–45 per cm, and an elongation rate in alongitudinal direction is 15–25%.

According to the structure above, by forming the crepes (wrinkles alongthe width direction of the sheet, a plurality of which are provided inthe longitudinal direction) and setting the elongation rate, in thelongitudinal direction, to be 12–25%, the thickness feeling, bulksoftness and massiveness upon usage are further enhanced, andparticularly, in case embossing is applied, this emboss is furtherdifficult to be flattened.

Further, a sanitary tissue paper roll according to one aspect of theabove-mentioned present invention is such that per each sheet ofsanitary tissue paper, grammage is 15–25 g/m², density is 0.10–0.15g/cm³, and thickness is 120–170 μm.

When particularly using such a sanitary tissue paper, the above andbelow mentioned effects will sufficiently be achieved.

Further, a sanitary tissue paper roll according to one aspect of theabove-mentioned present invention uses, as sanitary tissue paper, apaper made mainly of Nadelholz bleached kraft pulp and Laubholz bleachedkraft pulp and having a weight proportion of Nadelholz bleached kraftpulp to Laubholz bleached kraft pulp of 10:90–70:30.

The present invention can be preferably used for sanitary tissue paperrolls of such pulp products.

Further, a sanitary tissue paper roll according to one aspect of theabove-mentioned present invention is made by winding one sheet or twolayered sheets of sanitary tissue paper having been embossed.

The present invention is preferable for sanitary tissue paper rolls withembosses, and as described above, this applied emboss is difficult toflatten and will clearly remain upon usage, and thus, an effect isachieved in that a thickness feeling, bulk softness and/or massivenessare not easily lost.

Further, a sanitary tissue paper roll according to one aspect of theabove-mentioned present invention has a roll length of 58–65 m in a caseof winding one sheet of sanitary tissue paper, and a roll length is29–33 m in a case of winding two layered sheets of sanitary tissuepapers.

A preferable object of the present invention is a toilet paper roll, andin consideration of attaching the roll to a typical roll holder, it isnecessary for an outer diameter to be about 100–118 mm. According to arange of roll compressibility of the present invention, by setting aroll length within the above-mentioned range, it is possible to set theouter diameter within a range attachable to a typical roll holder.Further, in this case, the above-mentioned effects are also sufficientlyachieved.

Further, a sanitary tissue paper roll according to one aspect of theabove-mentioned present invention is made by winding sanitary tissuepaper around a core having an outer diameter of 30–40 mm.

As for a sanitary tissue paper roll, in addition to a cored type roll inwhich paper is wound around a paper core, there exists a non-cored typein which there is no core, and the present invention is applicable toboth types. According to the structure above, particularly for the caseof a cored-type roll, by setting the outer diameter of the core to be30–40 mm when taking the roll compressibility range of the presentinvention, it is possible to set an outer diameter within a rangeattachable to a typical roll holder. Further, in this case, theabove-mentioned effects are also sufficiently achieved.

The invention of a method of manufacturing a sanitary tissue paper rollaccording to another aspect of the present invention comprises: making asanitary tissue paper by setting a jet flow speed of pulp slurry/wirespeed ratio (J/W ratio) to be 0.92–1.00, winding one sheet ortwo-layered sheets of this paper, and obtaining a roll in which a rollcompressibility thereof is 0.68–0.74 m/cm², with the rollcompressibility being defined as a value obtained by dividing a rolllength by a cross section of the roll.

According to the structure above, by setting the jet flow speed of pulpslurry/wire speed ratio (J/W ratio) to be 0.92–1.00 upon making asanitary tissue paper, an amount of fiber oriented in a longitudinaldirection will be equal to at least an amount of fiber oriented in awidth direction, and thus, it will be possible to set alongitudinal-direction dry-state tensile strength of a manufactured rollto be 1.0–4.0 folds of a width-direction dry-state tensile strength.Therefore, the sanitary tissue paper will not easily be tightened into ahard, thin state upon winding or after winding, and thus, a thicknessfeeling, bulk softness and massiveness upon usage are sufficientlysecured. Particularly, in case embossing is applied to the sanitarytissue paper, this emboss is not easily flattened and will clearlyremain upon usage, and the thickness feeling, bulk softness andmassiveness will not easily be lost.

The invention of a sanitary tissue paper for a sanitary tissue paperroll according to another aspect of the present invention is suchwherein a sample paper is compressed between steel plates, whichrespectively have a circular surface with a compression area of 2 cm²,at a maximum compression load of 50 gf/cm², and upon returning of thispaper sample, a linearity of a displacement curve between a load and athickness is 0.2500–0.3300 for a one-ply, and 0.3400–0.3700 for atwo-ply, and a thickness upon a load of 50 gf/cm² is equal to at least0.1400 mm for a one-ply, and equal to at least 0.2500 mm for a two-ply.

According to the structure above, an appropriate flexible response willbe felt upon pushing with a hand.

In the invention of a sanitary tissue paper for a sanitary tissue paperroll according to one aspect of the above-mentioned present invention,it is possible that, a difference between thickness at a load of 0.5gf/cm² and a thickness at a load of 50 gf/cm² is equal to at least0.2000 mm for a one-ply, and equal to at least 0.2000 mm for a two-ply;and an amount of work upon compression is equal to at most 0.2000gf*cm/cm² for a one-ply, and equal to at most 0.2200 gf*cm/cm² for atwo-ply.

According to the structure above, paper quality will have bulk softness.

The invention of a sanitary tissue paper for a sanitary tissue paperroll according to another aspect of the present invention is suchwherein, in a relationship between curvature and flexural moment upon:chucking a paper sample having a width of 20 cm at a chuck distance of 1cm; bending the paper forward up to a maximum curvature of 2.5 cm⁻¹through pure bending by always keeping one side to form an arc; bendingthe paper back to its original position; bending the paper backwardly ata maximum curvature of −2.5 cm⁻¹; and returning the paper to itsoriginal position, an average value of a paper's bending resistance inlongitudinal and lateral directions is equal to at most 0.0080 gf*cm²/cmfor a one-ply, and equal to at most 0.0180 gf*cm²/cm for a two-ply, withthe paper's bending resistance being expressed as an average inclinationbetween a curvature of 0.5–1.5 cm⁻¹; and an average value of a paper'sflexural recoverability in longitudinal and lateral directions is0.0030–0.0050 gf*cm/cm for a one-ply, and 0.0130–0.0170 gf*cm/cm for atwo-ply, with the paper's flexural recoverability being expressed as anaverage hysteresis width of flexural moment between a curvature of0.5–1.5 cm⁻¹.

According to the structure above, resistance upon bending will be small,and the paper will have an appropriate bending recoverability.

The invention of a sanitary tissue paper for a sanitary tissue paperroll according to another aspect of the present invention is suchwherein an average value between an average deviation of a frictioncoefficient obtained for longitudinal and lateral directions on a frontside and that obtained for longitudinal and lateral directions on a backside for a one-ply is equal to at most 0.032, and, an average value forlongitudinal and lateral directions on a front side for a two-ply isequal to at most 0.029, with an average deviation of the frictioncoefficient being obtained upon: making a friction piece contact a papersample at a contact pressure of 10 gf, the friction piece being madefrom a piano wire of which a lateral section is 0.5 mm in diameter, andhaving a friction surface that is 5 mm long; and moving the frictionpiece 2 cm at a speed of 0.1 cm/second in a direction orthogonal to alength direction of the friction piece, while the paper sample hasapplied thereto a tension of 20 gf/cm in the moving direction; and also,an average value between a paper's average friction coefficient obtainedfor longitudinal and lateral directions on a front side and thatobtained for longitudinal and lateral directions on a back side for aone-ply is 0.2600–0.2800, and an average value of a paper's averagefriction coefficient for longitudinal and lateral directions on a frontside for a two-ply is 0.3500–0.3800.

According to the structure above, smoothness is provided since variationis small, and also, an appropriate frictional resistance is provided,and a stableness in terms of smooth feeling is provided.

Further, in a sanitary tissue paper for a sanitary tissue paper rollaccording to one aspect of the present invention, it is possible that,grammage is 15–25 g/m²; paper thickness is 120–180 μm;longitudinal/lateral ratio of tension is 2.0–3.0; elongation rate, in alongitudinal direction, is 20–35%; longitudinal tensile strength is110–115 N/m; and number of crepes is 30–50 per cm.

Examples

(A) First, a preferred embodiment will be explained in detail, withreference to the accompanying drawings, in view of the first object,which is to provide a sanitary tissue paper roll which can provide anappropriate tender-touch feeling when a consumer takes the roll inhis/her hand.

A toilet paper roll, which is the sanitary tissue paper roll in thepresent embodiment, is quantitatively measured according to the methodexplained below so that roll hardness will be within an appropriaterange as described below. Thus, it is possible to supply, to the market,toilet paper rolls which provide an appropriate tender-touch feeling tothe consumer.

FIG. 1 is a perspective view showing a measurement method for rollhardness of a toilet paper roll according to the present embodiment. Theroll hardness of a toilet paper roll 1 is quantitatively measuredaccording to the following steps:

(1) First, the toilet paper roll 1 is laid on a horizontal platform 5 sothat a central axis 1 a is in a horizontal direction.

(2) Then, a circular plate indenter 3, having an area of 2 cm² andassumed as an index finger of a person, is abutted against a center ofan upper surface of an outer periphery of a roll body.

(3) A pressing depth of the above-mentioned circular plate indenter 3 inthis abutted state is taken as zero, and this circular plate indenter 3is pressed vertically at a pressing pressure of 0.5 gf/cm² and apressing speed of 10 mm/minute.

(4) When a pressing depth of the above-mentioned indenter 3 becomesstable, the pressing depth is recorded as a first pressing depth.

(5) Then, continuously, the above-mentioned indenter 3 is verticallypressed at the same pressing speed and with a pressing pressureincreased to 50 gf/cm².

(6) When a pressing depth of the above-mentioned indenter 3 becomesstable, the pressing depth is recorded as a second pressing depth.

(7) A difference between the second pressing depth and the firstpressing depth (described as “difference in pressing depth”) is recordedas roll hardness, and then the pressing pressure on the above-mentionedindenter is released.

Note that, a first pressing (the pressing of above-mentioned (3)) amongthis two-step pressing operation is assumed as a pushing action by thefinger when the consumer takes a toilet paper roll in his/her hand. Onthe other hand, a second pressing (the pressing of above-mentioned (5))is assumed as a pushing action by the consumer when he pushes his/herfinger into the roll in order to check hardness of the roll that he isholding. That is, this consumer's action of checking the hardness of atoilet paper roll can be approximated by the above-mentioned two-steppressing operation, and, a feeling of the roll hardness the consumerreceives thereupon can be alternatively expressed through the differencein pressing depth.

The difference in pressing depth thus measured shows a high correlationwith a sensory-evaluation value of roll hardness actually felt by aperson. FIG. 2 shows a correlation diagram respectively for one-ply andtwo-ply toilet paper rolls having a roll width of 114 mm, and aninner/outer roll diameter of 40 mm/110 mm. Note that this correlationdiagram between difference in pressing depth and sensory-evaluationvalue has been obtained by having 50 people rate sensory-evaluationvalues of toilet paper rolls, which respectively have different valuesof difference in pressing depth, on a 1-to-5 scale (1: too hard, 2:slightly hard, 3: suitably soft, 4: rather too soft, 5: too soft).Plotted points on the correlation diagram representatively show only anaverage value of the sensory-evaluation values for each of the toiletpaper rolls in order to avoid complicity of the diagram.

From the diagram, it can be appreciated that the above-mentioneddifference in pressing depth has a good correlation with thesensory-evaluation value of roll hardness felt by a person. Note that acorrelation coefficient between the above-mentioned difference inpressing depth and the above-mentioned sensory-evaluation value (1–5) is0.79 for one-ply and 0.83 for two-ply, and, it can be concluded that theabove-mentioned difference in pressing depth can sufficiently be used asan evaluation index for alternatively expressing the roll hardness feltby a person.

Note that, although this correlation diagram concerns results for atoilet paper roll having an inner/outer roll diameter of 40 mm/110 mm, asimilar correlation was obtained when such correlation was checked forrolls having outer roll diameters of 100 mm and 120 mm respectivelyhaving varied inner roll diameters of 30 mm and 50 mm. Thus, it becameclear that a person feels the same hardness for a standard toilet paperroll with an outer roll diameter ranging in 100–120 mm and an inner rolldiameter ranging in 30–50 mm even if the inner/outer roll diameter isdifferent, as long as the difference in pressing depth is the same.Therefore, as for the above-mentioned standard toilet paper roll, it ispossible to uniquely and quantitatively evaluate the roll hardness feltby a person according to the difference in pressing depth regardless ofinner/outer roll diameter.

From such correlation diagrams, the difference in pressing depthcorresponding to a range in which a person has a suitably soft feel,that is, the range in which the above-mentioned sensory-evaluation valueis between 2.5–3.5, is between 2.5–3.5 mm for a two-ply toilet paperroll, and is between 1.5–2.5 mm for a one-ply roll. These areappropriate ranges for the difference in pressing depth. Therefore, bykeeping the difference in pressing depth of a toilet paper roll withinthe above-mentioned appropriate ranges, it becomes possible to providean appropriate tender-touch to a consumer who has taken the toilet paperroll. Thus, it is possible to supply, to the market, toilet paper rollswhich provide an appropriate tender-touch feeling to the consumer.

Note that, with regard to desirably for the toilet paper roll accordingto the present embodiment, as shown in FIG. 3, it is preferable thatnine measurement values of the difference in pressing depth, obtained bycontinuously conducting the above-mentioned measurement nine times, areall within the above-mentioned appropriate ranges and that a differencebetween a maximum and minimum of the above-mentioned measurement valuesis within a range of 0.5–1.0 mm. This is because if the above-mentioneddifference between the maximum and minimum of the above-mentionedmeasurement values exceeds 1.0 mm, the roll is easily subjected topermanent deformation and a shape-maintaining ability is deteriorated;whereas if the difference is below 0.5 mm, permanent deformation isdifficult to occur and the roll feels hard. To the contrary, if theabove-mentioned difference is within the 0.5–1.0 mm range, restorabilityand an ability to deform permanently will be appropriate; that is, theroll will have both an appropriate shape-maintaining ability and softfeel and be superior not only in its sense of touch but also in itsappearance, and thus, it will be possible to appeal to a consumer'ssense of beauty. The number of times of measurement is set at nine timesbecause a minimum value of the difference in pressing depth willsufficiently settle to a constant value through nine times ofmeasurement.

Further, it is desirable that a sheet (sanitary tissue paper) having anelongation rate, in a longitudinal direction, of 20–35% is used for theabove-mentioned toilet paper roll. Accordingly, it is possible tofacilitate manufacturing of the toilet paper roll. Here, “elongationrate” is an amount of elongation per unit length in a longitudinaldirection when tension is imparted in longitudinal direction until thesheet shears. This amount of elongation is mainly due to the crepes(wrinkles along a width direction of the sheet, a plurality of which areprovided in the longitudinal direction) as appreciated from a sidesection of the sheet shown in FIG. 4. The elongation rate becomes smallas a dimension of the crepes or waves becomes large or the number ofcrepes per unit length decreases, as shown in FIG. 4( a); whereas, theelongation rate becomes large as the above-mentioned waves become smallor the above-mentioned number of crepes increases, as shown in FIG. 4(b).

In case a sheet having a small elongation rate below 20% is used, whenthe sheet is wound into a roll with a constant winding tension, sincethe crepes are fully stretched and no elongation remains as seen in FIG.5( a), bulkiness becomes small and the roll becomes hard. On the otherhand, if the sheet is wound with a low roll compressibility to maintainelongation in order to avoid the above-mentioned situation, since thecrepes are small as seen in FIG. 5( b), a space tends to be createdbetween the sheets and winding becomes loose, resulting in that the rollis easily deformed by, for example, lateral protrusion of a side-endsurface of the roll in a telescopic manner. That is, in the case of asheet having an elongation rate below 20%, it is difficult to achieveboth setting the above-mentioned difference in pressing depth, whichexpresses the roll hardness, within the above-mentioned appropriaterange, and maintaining a shape of the roll.

Further, in case a sheet having a large elongation rate exceeding 35% isused, the crepes remain too large when the sheet is wound into a roll,resulting in that bulkiness becomes too large and the roll becomesexcessively soft. Therefore, it is difficult to set the above-mentioneddifference in pressing depth within the above-mentioned appropriaterange.

Contrary to the above, if a sheet having an appropriate elongation rateof 20–35% is used, since the crepes remain to have an appropriate sizeas those shown in FIG. 5( c) even when the sheet is wound into a roll,bulkiness can be set to an appropriate extent, and a difference inpressing depth can easily be set within the above-mentioned appropriaterange. Further, since the sheets, which are stacked in a radialdirection, are resiliently bound together because of the crepesremaining in an appropriate size, side-end surfaces will not easilyprotrude laterally in a telescopic manner, and a roll-shape-maintainingability is superior. That is, it is possible to achieve both setting theabove-mentioned difference in pressing depth within the appropriaterange, and maintenance of a shape of the roll. Therefore, it is possibleto facilitate manufacturing of toilet paper rolls.

Note that the above-mentioned elongation rate can be varied accordingto, for example, material, strength and humidity. For example, regardingmaterial, the elongation rate will increase if the below-described NBKPmixing rate is high, and also, the elongation rate will increase ifbeating is performed and tensile strength is increased.

Below, explanation will be made of a manufacturing specification of atoilet paper roll preferable for setting a difference in pressing depthwithin the above-mentioned appropriate range.

(1) A sheet has a grammage of 15–25 g/m², and its paper thickness is120–160 μm per sheet.

(2) A longitudinal/lateral ratio of dry-state tensile strength of thesheet is 2.0–4.0. Here, “dry-state tensile strength” is tensile strengthmeasured according to tensile-characteristic testing method defined byJapan Industrial Standard, JISP8113. The “longitudinal/lateral ratio ofdry-state tensile strength” indicates a ratio obtained by dividing thedry-state tensile strength in a longitudinal direction by the dry-statetensile strength in a width direction. Here, a tensile-characteristictesting method defined by JISP8113 will be explained. Firstly, a 25mm-wide sheet, taken as a test piece, is placed in an atmosphere definedby JISP8111 (an atmosphere with a temperature of 23±1° C. and humidityof 50±2%), and is left in this state until the temperature and humidityof the above-mentioned test piece reaches an equilibrium. When anequilibrium is reached, both sides, in a longitudinal direction, of thetest piece are pinched with an interval of 180±1 mm, and the test pieceis pulled at a constant speed of 20±5 mm/minute until the piece shears.A maximum load thereupon is converted to a value per width to thusobtain the above-mentioned tensile strength.

A sheet having such a longitudinal/lateral ratio can be manufactured byadjusting a jet flow speed of pulp slurry/wire speed ratio (J/W ratio),and appropriately adjusting an amount of fiber oriented in thelongitudinal direction to be more than an amount of fiber oriented inthe width direction.

Here, “jet flow speed of pulp slurry” is a flow speed right afterjetting of a pulp feedstock onto an endless wire along its travelingdirection during a papermaking process (which is a process of making athin, continuous sheet of uniform thickness by flowing a pulp feedstock,made by including pulp in water, onto a traveling endless wire andmaking paper). Further, “wire speed” is a traveling speed of theabove-mentioned endless wire.

(3) An NBKP mixing rate in pulp feedstock is 20–60%. Here, “NBKP mixingrate” indicates a weight proportion of Nadelholz bleached kraft pulp(NBKP) in the above-mentioned pulp feedstock, which is composed ofNadelholz bleached kraft pulp (NBKP) and Laubholz bleached kraft pulp(LBKP). With the above mentioned NBKP mixing rate, it is possible tomake a sheet enhanced both in terms of strength due to use of Nadelholzbleached kraft pulp, and soft tender-touch due to use of Laubholzbleached kraft pulp. Note that the feedstock is not limited only topulp, and used-paper feedstock can be used.

(4) The sheet has been subjected to an embossing process. Through thisembossing process, since rigidity of the sheet can be enhanced, it ispossible to make the roll have an appropriate roll hardness even underconditions where roll compressibility is low. Thus, a range of rollcompressibility for achieving the above-mentioned difference in pressingdepth can be broadened.

(5) The roll compressibility of the roll is 0.68–0.74 m/cm². Here, “rollcompressibility” is a value obtained by dividing roll length of the rollby an area of a side-end surface of the roll (i.e., an area of a surfaceorthogonal to a central axis of the roll). Adjustment of the rollcompressibility can be accomplished by adjusting a winding tensionapplied to the sheet upon winding the sheet into a roll.

-   -   (6) The roll length of the roll is 58–65 m for one-ply, 29–33 m        for two-ply, and 19–22 m for three-ply.

Note that an inner/outer roll diameter is within a range where the innerdiameter is 30–50 mm, and the outer diameter is 100–120 mm, as explainedabove.

Tables 1 and 2 show manufacturing specifications and roll hardness ofone example of a toilet paper roll manufactured according to theabove-mentioned manufacturing specification, compared to commercialtoilet paper rolls now on the market. Note that Table 1 is of a two-plytoilet paper roll, and Table 2 is of a one-ply roll. Both commercialtwo-ply and one-ply rolls have a difference in pressing depth which isnot within the above-mentioned appropriate range. Further, an averagevalue of a sensory-evaluation value obtained from the above-mentioned 50persons, shown at the bottommost rows in Tables 1 and 2, is not withinthe range of 2.5–3.5 which provides a suitably soft feel. To thecontrary, results for both the one-ply and two-ply rolls according tothe present example are satisfactory: a difference in pressing depth iswithin the above-mentioned appropriate range, and sensory-evaluationvalues are 3.4 and 2.9, respectively. Further, as for a differencebetween a maximum and minimum of measurement values obtained bycontinuously measuring the above-mentioned difference in pressing depthnine times, the values for the commercial rolls are not in the range of0.5–1.0 mm. To the contrary, since the present example is within theabove-mentioned range and is provided with an appropriateshape-maintaining ability in addition to the above-mentioned suitablesoft feel, the rolls will not easily be deformed in shape when displayedin stores and will have a superior appearance.

TABLE 1 Commercial Commercial Commercial Commercial two-ply Exampleproduct 1 product 2 product 3 product 4 MANUFACTURING Grammage (g/m²)16.5 16.5 16.3 16.4 15.3 SPECIFICATION Paper thickness (μm) 141 138 118137 110 Elongation rate (%) 24.5 16.3 15.1 16.3 12.2 NBKP mixing rate(%) 30 30 — — — Inner roll diameter (mm) 38 45 — — — Outer roll diameter(mm) 109 110 — — — Roll length (m) 30 — — — 40 Roll compressibility(m/cm²) 0.73 0.76 — — 1.01 Presence of emboss present — — — —Longitudinal-direction 298 372 299 295 237 dry-state tensile strength(CN) Lateral-direction 125 147 93 106 59 dry-state tensile strength (CN)Tensile strength 2.38 2.53 3.22 2.78 4.02 longitudinal/lateral ratioROLL HARDNESS Difference in 2.9 1.8 4.6 1.9 1.6 pressing depth (mm)Difference between maximum 0.7 0.4 1.3 0.4 0.4 and minimum of differencein pressing depth measured nine times (mm) Sensory-evaluation value(average) 3.4 2.1 3.8 2.4 1.2

TABLE 2 Commercial Commercial Commercial Commercial one-ply Exampleproduct 1 product 2 product 3 product 4 MANUFACTURING Grammage (g/m²)20.2 — 20.5 19.3 20 SPECIFICATION Paper thickness (μm) 136 130 127 140162 Elongation rate (%) 26.2 18.1 10.5 17.9 19 NBKP mixing rate (%) 3030 — — — Inner roll diameter (mm) 38 45 — — — Outer roll diameter (mm)109 110 — — — Roll length (m) 60 — — — — Roll compressibility (m/cm²)0.73 0.76 — — — Presence of emboss present — — — —Longitudinal-direction 311 359 233 285 300 dry-state tensile strength(CN) Lateral-direction 110 103 102 104 100 dry-state tensile strength(CN) Tensile strength 2.83 3.49 2.28 2.74 3 longitudinal/lateral ratioROLL Difference in 1.6 1.4 3.4 1.3 1.1 HARDNESS pressing depth (mm)Difference between maximum 0.5 0.4 1.2 0.4 0.3 and minimum of differencein pressing depth measured nine times (mm) Sensory-evaluation value(average) 2.9 24 42 2.4 1.7

(B) Next, a preferred embodiment will be explained in detail, withreference to the accompanying drawings, in view of the second object,which is to provide a sanitary tissue paper roll which is rich inthickness feeling and bulk softness while being difficult to deform,which has a sufficient massiveness when taken in the hand, and in whichan emboss is not easily flattened in case embossing is applied.

Note that, although the embodiments of the present invention aredescribed in detail regarding examples of toilet paper rolls havingcores, it is of course possible to apply the present invention to othersanitary tissue paper rolls such as toilet paper rolls without cores,and kitchen paper rolls.

FIG. 6 shows an example of a cored toilet paper roll 1 made by winding aone sheet or two-layered sheets of sanitary tissue papers P around acore 1A such as a paper core. Meanings of terms of the present inventionwill be defined: “roll length” is a length of sanitary tissue paper P ina winding direction (longitudinal direction), “roll cross section” is anarea of a surface orthogonal to a central axis of the roll (which isequal to an area of a side plane 1S), and “width direction” is adirection parallel to a direction of the central axis (or a directionorthogonal to the longitudinal direction).

In the present invention, a roll is formed so that roll compressibility,which is a value determined by dividing the roll length of the roll bythe roll cross section, is 0.68–0.74 m/cm². A particularly appropriaterange of roll compressibility is 0.70–0.74 m/cm². Adjustment of the rollcompressibility can be accomplished by adjusting tension applied to thesanitary tissue paper P upon winding. As described above, if the rollcompressibility exceeds 0.74 m/cm², winding will be too hard causingloss of embosses and loss of thickness feeling and/or bulk softness;whereas if the roll compressibility is below 0.67 M/cm², windings willloosen, the roll will tend to deform in a telescopic manner, itssectional shape will easily deform in to a polygonal shape, andmassiveness when taken in the hand will be lost.

As for strength of the sanitary tissue paper P per sheet, it isdesirable to heighten a width-direction dry-state tensile strength,which is measured according to the tensile-characteristic testing methoddefined by JISP8113, to a necessary-and-sufficient extent equal to atleast 40 N/m, and desirably 40–45 N/m; and also, it is desirable to seta longitudinal-direction dry-state tensile strength to 1.0–4.0 folds,and desirably 2.5–3.5 folds of the width-direction dry-state tensilestrength. Through such a structure, the sanitary tissue paper P will noteasily be tightened into a hard, thin state upon winding or afterwinding, and thus, a thickness feeling, bulk softness and massivenessupon usage are sufficiently secured, even if the roll compressibility isset to be 0.68–0.74 M/cm². Particularly, in case embossing (not shown)is applied to the sanitary tissue paper P, this emboss is not easilyflattened and will clearly remain upon usage, and the thickness feeling,bulk softness and massiveness will not easily be lost.

In order to manufacture such sanitary tissue paper P, it is recommendedfor a jet flow speed of pulp slurry/wire speed ratio (J/W ratio) to be0.92–1.00 upon papermaking. Through such a structure, an amount of fiberoriented in the longitudinal direction will be equal to at least anamount of fiber oriented in the width direction, and thus, it will bepossible to set the longitudinal-direction dry-state tensile strength ofa manufactured roll to be 1.0–4.0 folds of the width-direction dry-statetensile strength.

Regarding the core 1A used for the cored-type roll, as is well known, apaper core made of cardboard with a thickness of about 0.5 mm ispreferable. However, it is also possible to use a core made, forexample, of resin. It is preferred for the paper core 1A to have aninner diameter of about 30–40 mm. A diameter of a shaft of ashaft-mounting type roll holder, or a width of a holding piece of aone-touch type roll holder, is about 20–25 mm, and thus, a paper corewith an inner diameter at most equal to than 30 mm will not fit well, orwill not rotate with ease. Further, if an inner diameter of the papercore becomes small, twisting may occur in the paper core upon rollwinding, which may be a cause of defectively wound items.

Further, it is desirable for the sanitary tissue paper P constitutingthe roll of the present invention to have a grammage of 15–25 g/m²,density of 0.10–0.15 g/cm³, and a thickness of 120–170 μm, andparticularly 160–170 μm, per sheet.

Particularly, in this type of sanitary tissue paper roll, there arecases where crepes (wrinkles along the width direction of the sheet, aplurality of which are provided in the longitudinal direction) areapplied. The present invention may adopt such a structure, and it ispreferable that the number of crepes is 25–45 per cm, particularly 42–45per cm, and an elongation rate in the longitudinal direction is 15–25%,preferably 22–25%.

Further, as for the sanitary tissue paper P constituting the roll of thepresent invention, it is desirable to use a paper made mainly ofNadelholz bleached kraft pulp (NBKP) and Laubholz bleached kraft pulp(LBKP), and having a weight proportion of Nadelholz bleached kraft pulpto Laubholz bleached kraft pulp of 10:90–70:30. Particularly, by settingthis NBKP: LBKP rate to be within a range of 1:2–1:3, it is possible toachieve both an enhancement in strength, which is caused by usingNadelholz bleached kraft pulp, and an enhancement in soft tender-touch,which is caused by using Laubholz bleached kraft pulp.

Furthermore, in the present invention, it is possible to enhance athickness feeling and bulk softness by using a sanitary tissue paper Phaving been embossed. As described above, although sanitary tissue paperrolls with embosses have been known, this embossing is stretched andflattened, and a thickness feeling and bulk softness are lost uponwinding or as time passes due to tension in a winding direction. To thecontrary, since the roll of the present invention has a rollcompressibility of 0.68–0.74 m/cm², an applied emboss is not easilyflattened and will clearly remain upon usage, and a thickness feeling,bulk softness and massiveness will not be lost easily. Note that it ispossible to adopt known embossing methods and emboss shapes and/orarrangements. Specifically, it is possible to adopt, before winding, amethod of forming embosses in which a sanitary tissue paper is passedbetween a steel roll having emboss patterns and a rubber roll andpressurized, or, a method of forming embosses in which a sanitary tissuepaper is passed between a steel roll having male emboss patterns and asteel roll having female emboss patterns and pressurized.

Further, in case of application to toilet paper rolls as in the presentexample, it is desirable that an outer roll diameter is about 100–118mm. Particularly, it is desirable that the outer diameter is 110–115 mm,in order to facilitate holding a roll in a roll holder and facilitaterotation of the roll upon usage.

For this reason, in the present invention, roll length for a one-plyproduct may be 58–65 m, and roll length for a two-ply product may be29–33 m, and, an outer diameter of the core 1A may be 30–40 mm, andparticularly, preferably 36–39 mm.

Below, effects of the present invention will be explained throughexamples.

As shown in Table 3 and Table 4, various types of toilet paper rolls aremanufactured or obtained. A measurement for tensile strength isperformed, and also, tender-touch, bulk softness, thickness feeling,appearance of embosses (remaining state of the embosses), and roll shapeand massiveness were respectively evaluated on a 1-to-5 scale by 50people, and an average value was taken as an evaluation value.Measurement results and evaluation results are also shown in Table 3 andTable 4.

TABLE 3 Com- Com- Com- Com- Com- Com- Com- parative parative mercialmercial mercial mercial mercial Example 1 Example 2 Example 1 Example 2Product 1 Product 2 Product 3 Product 4 Product 5 MANUFAC- TYPE one-plytwo-ply one-ply two-ply one-ply one-ply one-ply one-ply one-ply TURINGGrammage (g/m²) 20.5 16.8 20.5 16.6 20.5 19.2 19 27.2 35.5 CONDITIONPaper thickness (μm) 142 128 139 133 120 134 144 187 247 Density (g/cm³)0.144 0.131 0.147 0.125 0.171 0.143 0.132 0.145 0.144 Paper core 38 3845 45 45 45 45 35 35 inner diameter (mm) Roll length (m) 60.4 60.5 60.460.4 60.9 60.9 60.4 57.87 45.59 Outer diameter (mm) 109 111 110 109.2111.3 110.7 109.4 126.1 126.3 Roll compressibility 0.743 0.714 0.7710.784 0.755 0.765 0.781 0.505 0.396 (m/cm2) NBKP:LBKP 32:68 26:74 25:7533:67 — — — — — J/W ratio 0.96 0.99 0.91 0.9 — — — — — upon papermakingTENSILE Longitudinal-direction 113 149 128 163 116 127 122 95.2 85.6TEST dry-state tensile strength (N/m) Width-direction 43 47 38 42 36 4438 56.8 58.4 dry-state tensile strength (N/m) Tensile strength ratio 2.63.2 3.4 3.9 3.22 2.89 3.21 1.68 1.47 SENSORY Tender-touch 4 4.1 2.8 3.33.1 3 3 3.5 4.1 EVALUATION Bulk Softness 3.9 4.3 2.7 2.7 2.5 3.1 3 3.93.4 Thickness feeling 3.8 3.8 2.6 2.8 2.3 3.4 3.3 4.1 4.5 Embossappearance 4.1 4.2 3.2 3.3 2.4 3.4 3.2 3.4 3.2 Roll shape, 4 4.3 3.5 3.63.4 3.5 3.5 2.8 2 Massiveness

TABLE 4 Commercial Commercial Commercial Commercial CommercialCommercial Commercial Product 6 Product 7 Product 8 Product 9 Product 10Product 11 Product 12 MANUFACTURING TYPE one-ply two-ply two-ply two-plytwo-ply two-ply two-ply CONDITION Grammage (g/m²) 25.1 16.5 15.7 16.318.1 16.4 19.8 Paper thickness (μm) 125 115 110 135 110 85 120 Density(g/cm³) 0.201 0.143 0.143 0.121 0.165 0.193 0.165 Paper core 35 45 45 4540 35 35 inner diameter (mm) Roll length (m) 96.87 60.8 81 60.6 45.24128.02 69.7 Outer diameter (mm) 125.4 110.8 111.1 109.4 107.1 122.8122.3 Roll compressibility 0.855 0.762 1.009 0.784 0.589 1.183 0.65(m/cm²) NBKP:LBKP — — — — — — — J/W ratio — — — — — — — upon papermakingTENSILE Longitudinal-direction 71.2 119 109 142 141.6 162.4 114 TESTdry-state tensile strength (N/m) Width-direction 51.6 40 29 51 57.2 44.448 dry-state tensile strength (N/m) Tensile strength ratio 1.38 2.983.76 2.78 2.48 3.66 2.38 SENSORY Tender-touch 3.9 3 3.3 3 3.8 2.2 4.1EVALUATION Bulk Softness 3.8 3.1 2.7 3.1 3 2 3.8 Thickness feeling 3.82.8 2.4 3.1 2.5 2.2 3 Emboss appearance 2.7 2.4 2.9 3 2.2 2 3.5 Rollshape, Massiveness 3.3 3 3.5 3 2 3.4 2.6

It is apparent from Table 3 and Table 4 that examples 1 and 2 accordingto the present invention are superior in terms of tender-touch, bulksoftness, thickness feeling, appearance of embosses (remaining state ofthe embosses), and roll shape and massiveness, compared to comparativeexamples 1 and 2 and to commercial products.

(C) Finally, a preferred embodiment will be explained in detail, withreference to the accompanying drawings, in view of the above-mentionedthird object, which is to provide a sanitary tissue paper for a sanitarytissue paper roll which is superior and matches human sensoryevaluation, and which is highly valued in terms of such sensoryevaluation. Note that a one-ply (single sheet) product is indicated as1P, and a two-ply (double sheet) product is indicated as 2P. Further,grammage, elongation rate and tensile strength (longitudinal/lateralratio of tension) are measurement values according to JIS. Paperthickness is measured using a dial thickness gauge “PEACOCK type-G”available from Ozaki Manufacturing Co., Ltd. under conditions of JIP P8111. Specifically, after checking that there is no dust, dirt or suchbetween a plunger and a measuring platform, the plunger is lowered ontothe measuring platform, and a scale of the above-mentioned dialthickness gauge is moved to set a zero point. Then, the plunger israised, a sample (tissue paper) is placed on the measuring platform, theplunger is slowly lowered, and a current gauge is read. Here, theplunger is only to be placed onto the sample. Note that measurement isperformed for one sheet, and an average value for ten measurements istaken. Although a model of a characteristic-testing machine will bementioned below, similar machines which basically adopt the samemeasurement principle can also be used.

The present inventors found that it is desirable to take the threecharacteristics below as an evaluation standard, and found that,regarding actual toilet paper rolls and/or toilet papers, onessatisfying as many of the below-defined characteristics as possible havea higher commercial value.

(1) Compression Characteristics: LC, TM, WC, and (T0–TM)

A “Handy compression tester KES-G5” available from Katotech Co., Ltd.was used for this compression-characteristic test. A paper sample iscompressed between steel plates, which respectively have a circularsurface with a compression area of 2 cm², at a maximum compression loadof 50 gf/cm², and an evaluation is made of a compression characteristicupon returning of the paper sample. Regarding a compressioncharacteristic thereupon shown in FIG. 7, as for the present invention,a linearity of a displacement curve between load and thickness is to be0.2500–0.3300 for one-ply, and 0.3400–0.3700 for two-ply.

Here, “linearity” (compression hardness) LC indicates a ratio betweendiagonally-shaded area S in FIG. 7 and area of Δ ABC. LC signifieslinearity of a flexible response in view of pressing depth, and thelinearity is high and a value is high for hard materials. The above is avalue range in which an appropriate flexible response is felt uponpushing with a hand.

Further, as for the present invention, thickness TM upon load of 50gf/cm² is to be equal to at least 0.1400 mm for one-ply, and equal to atleast 0.2500 mm for two-ply.

Note that, it is desirable that a difference (T0–TM) between thicknessT0 upon load 0.5 gf/cm² and the thickness TM upon load 50 gf/cm² isequal to at least 0.2000 mm for one-ply, and equal to at least 0.2000 mmfor two-ply. As T0–TM increases, a pressing depth when pressing up to 50gf/cm² is large, and this indicates a paper quality with bulk softness.Further, it is desirable that an amount of work upon compression WC isequal to at most 0.2000 gf*cm/cm² for one-ply, and equal to at most0.2200 gf*cm/cm² for two-ply.

(1) Bending Characteristics: B and 2HB

An “automatic, pure-bending tester KESFB2-AUTO-A” available fromKatotech Co., Ltd. was used for this compression-characteristic test. Asshown in FIG. 8, a paper sample having a width of 20 cm is chucked at achuck distance of 1 cm, is bent forward up to a maximum curvature of 2.5cm⁻¹ through pure bending by always keeping one side to form an arc, andis bent back to its original position. Then, the sample is bentbackwardly at a maximum curvature of −2.5 cm⁻¹, and then is returned tothe original position. A relationship between the curvature and aflexural moment during the above is evaluated.

This relationship is obtained as a value on a hysteresis curve shown inFIG. 9. A paper's bending resistance B is expressed as an averageinclination between a curvature of 0.5–1.5 cm⁻¹, and in the presentinvention, an average value thereof (B average) in longitudinal andlateral directions is made to be equal to at most 0.0080 gf*cm²/cm forone-ply, and equal to at most 0.0180 gf*cm²/cm for two-ply. The largerthe average value of bending resistance B (B average) s, the harder thesample and the more difficult it is to bend. According to a range of thepresent invention, resistance in bending is small.

Further, a paper's flexural recoverability (2HB) is expressed as anaverage hysteresis width of flexural moment between the curvature of0.5–1.5 cm⁻¹, and here, an average value thereof (2HB average) in thelongitudinal and lateral directions is to be 0.0030–0.0050 gf*cm/cm forone-ply, and 0.0130–0.0170 gf*cm/cm for two-ply. The larger the averagevalue of flexural recoverability 2HB (2HB average) the lower or inferiora recoverability upon bending. The present invention defines a valuerange which indicates an appropriate recoverability in bending.

(3) Surface Characteristics: MMD and MIU

A “friction sensitivity tester KESSE” available from Katotech Co., Ltd.can be used for this surface characteristic test. For this measurement,as shown in FIG. 10, a friction piece is made from a piano wire, ofwhich a lateral section is 0.5 mm in diameter, and has a frictionsurface that is 5 mm long. The friction piece is made to contact a papersample at a contact pressure of 10 gf, and is moved 2 cm at a speed of0.1 cm/second while this paper sample is being applied with a tension of20 gf/cm in a moving direction, and a friction coefficient thereupon ismeasured.

In the present invention, two values are measured: an average frictioncoefficient MIU which is an average value of the friction coefficientupon movement of the friction piece, and an average deviation of thefriction coefficient upon this movement MMD (a value obtained bydividing an integral, which is calculated by integrating a deviationfrom an average value of the friction coefficient upon theabove-mentioned movement across the above-mentioned movement distance (2cm), by the above-mentioned movement distance).

In the present invention, an average value (front and back average MMD)between average deviations MMD of the above-mentioned frictioncoefficient obtained for longitudinal and lateral directions on a frontside and that obtained for longitudinal and lateral directions on theback side for a one-ply is equal to at most 0.0320, and, an averagevalue thereof (front average MMD) for longitudinal and lateraldirections on a front side for a two-ply is equal to at most 0.0290.According to the present invention, since there is small variation invalue, a smooth feeling is provided.

Further, the average value (front and back average MIU) between thepaper's average friction coefficient MIU obtained for the longitudinaland lateral directions on the front side and that obtained for thelongitudinal and lateral directions on the back side for a one-ply is0.2600–0.2800, and the average value (front average MIU) of the paper'saverage friction coefficient for the longitudinal and lateral directionson the front side for two-ply is 0.3500–0.3800. According to the presentinvention, an appropriate frictional resistance is provided, and astableness in smooth feeling is provided.

By setting measurement values of six items, (1) compression hardness,(2) thickness at maximum load, (3) bending resistance, (4) flexuralrecoverability, (5) surface friction coefficient, and (6) averagedeviation of surface friction coefficient, within a predetermined range,it is possible to reproduce quality characteristics required for atoilet paper.

The compression characteristics can be adjusted according to, forexample, LBKP and NBKP mixing ratio and/or a type of pulp (coarseness offiber, or a type or age of tree to be feedstock) of the feedstock,beating degree, reel moisture content, and/or a gap/pressure/material ofa calender. It is desirable that no used-paper pulp is mixed.

The bending characteristics can be adjusted according to, for example,tensile strength, longitudinal/lateral ratio, crepe shape (rate ofcrepes, height difference of crepes, and such), water content rate,density, and/or adding of a paper-strengthening agent.

The surface characteristics can be adjusted according to, for example,pulp mixture, conditions of the calender, reel moisture content, angleof doctor blade tip, blade angle, balance of bond/peeling strength,and/or rate of crepes.

Regarding the above three characteristics, when one of thecharacteristics changes, the others will change as well. Thus, it isdifficult to control these characteristics. By converting thesecharacteristics into numerals and grasping their correlation as dataindicating a change in each of these quality characteristics occurringupon change in manufacturing conditions, it becomes possible toreproduce a toilet paper quality requested by a consumer.

Below, effects of the present invention will be explained throughexamples.

The above-mentioned three types of characteristic tests and obtainmentof six data were repeated, and correspondence with a sensory evaluationby 10 adults was researched. This sensory evaluation shows averagevalues regarding a 1-to-4 scale evaluation regarding “thickness feeling(rich, thick feel)”, “tender-touch” and “smoothness”, and higher valuesindicate a higher rating. Further, a total evaluation shows averagevalues regarding a similar 1-to-4 scale evaluation regarding whether ornot a toilet paper is preferable considering all matters. All of thecomparative examples are current commercial products.

(1) Results regarding the compression characteristics: LC, TM, WC AND(T0–TM) are shown in Table 5. Note that Table 5 also shows a totalevaluation, paper-quality data, and other characteristics.

TABLE 5 Compression-characteristics WC Thick- Total Paper LongitudinalLateral Longitudinal/ Soft- TM TO-TM gf * cm/ ness evalu- Grammagethick- tension tension Lateral ness LC mm mm cm² feeling ation g/m² nessμm N/m N/m ratio T/Y cN Toilet Present 0.2500~ >0.1400 >0.2000 <0.20001P invention 0.3300 Example 1 0.3167 0.1463 0.2213 0.1757 2.74 2.9 20.4138 112 33 3.43 3.43 Comparative 0.3437 0.1383 0.21 0.1797 2.52 2.6820.3 139 128 38 3.37 4.5 Example 1 Comparative 3.51 0.1487 0.2613 0.28832.61 2.55 19.3 144 113 32 3.53 3.89 Example 3 Comparative 0.375 0.1560.217 0.2013 2.52 2.26 20 147 114 33 3.45 4.04 Example 4 Comparative0.291 0.1293 0.2202 0.2347 2.16 1.9 20.5 109 120 54 2.22 4.02 Example 5Comparative 0.4367 0.1247 0.0933 0.1017 1.94 1.32 19.9 128 229 42 5.543.89 Example 6 Toilet Present 0.3400~ >0.2500 >0.2000 <0.2200 2Pinvention 0.3700 Example 2 0.3467 0.2635 0.2335 0.203 3.42 3.35 16.1 133114 46 2.45 2.18 Example 3 0.361 0.2613 0.2303 0.2167 3.48 3.35 16.1 140136 59 2.31 2.49 Comparative 0.388 0.253 0.2253 0.2153 3.48 3.45 16.6141 156 53 2.96 2.3 Example 7 Comparative 0.3527 0.2317 0.264 0.22332.97 2.77 16.4 137 140 49 2.85 2.41 Example 8 Comparative 0.4587 0.23930.2767 0.3163 2.77 2.48 15.5 137 125 42 2.97 2.75 Example 9 Comparative0.5613 0.3263 0.3314 0.465 2.55 2.19 15.4 136 112 33 3.39 2.74 Example10 Comparative 0.348 0.206 0.3143 0.2727 3.1 2.68 16.6 113 130 41 3.172.46 Example 11 Comparative 0.2237 0.1867 0.382 0.2133 3.1 3.19 15.4 11095 24 4.02 1.75 Example 12 Comparative 0.4763 0.2407 0.3166 0.3747 1.91.35 16.8 138 245 84 2.91 3.79 Example 13

(2) Results regarding bending characteristics: B and 2HB are shown inTable 6.

TABLE 6 Bending-characteristics Longitudinal Lateral Average B 2HB B 2HBB 2HB Tender gf * cm²/cm gf * cm/cm gf * cm²/cm gf * cm/cm gf * cm²/cmgf * cm/cm touch Toilet 1P Present <0.0080 0.0030~0.0050 inventionExample 1 0.0086 0.005 0.0066 0.0035 0.0076 0.0043 3.13 Comparative0.0094 0.0047 0.0078 0.0039 0.0086 0.0043 2.74 Example 1 Comparative0.0119 0.008 0.0083 0.0056 0.0101 0.0068 2.52 Example 2 Comparative0.0106 0.0067 0.0066 0.0045 0.0086 0.0056 2.45 Example 3 Comparative0.0117 0.0078 0.0112 0.0047 0.0115 0.0063 1.97 Example 4 Comparative0.0099 0.0073 0.0085 0.0043 0.0092 0.0058 1.71 Example 5 Toilet 2PPresent <0.0180 0.0130~0.0170 invention Example 2 0.02 0.0203 0.01380.0111 0.0169 0.0157 3.61 Example 3 0.0184 0.0206 0.0133 0.0108 0.01590.0157 3.61 Comparative 0.0202 0.022 0.0146 0.0121 0.0174 0.0171 3.45Example 6 Comparative 0.0246 0.02 0.0153 0.0123 0.2 0.0162 2.94 Example7 Comparative 0.0215 0.0177 0.019 0.0134 0.0203 0.0156 2.74 Example 8Comparative 0.0244 0.019 0.0189 0.0265 0.0217 0.0228 2.39 Example 9Comparative 0.0245 0.02 0.0223 0.0179 0.0234 0.019  2.97 Example 10Comparative 0.0114 0.0085 0.0192 0.0135 0.0153 0.011  3.39 Example 11Comparative 0.0321 0.0339 0.0322 0.0316 0.0322 0.0328 1.48 Example 12

(3) Results regarding surface characteristics: MMD and MIU are shown inTable 7 and Table 8.

TABLE 7 Surface-characteristics Front Back MMD front MMD front MMD frontMMD back MMD back MMD back MMD longitudinal lateral average longitudinallateral average average Smoothness Toilet 1P Present <0.032 inventionExample 1 0.033 0.026 0.0295 0.0346 0.03 0.0323 0.0309 3.23 Comparative0.0366 0.0283 0.0325 0.0357 0.0305 0.0331 0.0328 2.71 Example 1Comparative 0.0383 0.0257 0.032 0.036 0.0293 0.0327 0.0323 2.58 Example3 Comparative 0.0404 0.0235 0.032 0.041 0.0293 0.0352 0.0336 2.32Example 4 Comparative 0.043 0.027 0.035 0.0424 0.0266 0.0345 0.0348 2.06Example 5 Comparative 0.0446 0.0321 0.0384 0.054 0.0373 0.0457 0.0421.61 Example 6 Toilet 2P Present <0.029 invention Example 2 0.03180.0252 0.0285 3.61 Example 3 0.0282 0.0212 0.0247 3.61 Comparative 0.0330.0261 0.0296 2.52 Example 7 Comparative 0.0331 0.0254 0.0293 3 Example8 Comparative 0.0283 0.0213 0.0248 2.81 Example 9 Comparative 0.02740.0268 0.0271 2.26 Example 10 Comparative 0.0289 0.0254 0.0272 3.1Example 11 Comparative 0.0245 0.0185 0.0215 3.68 Example 12 Comparative0.0439 0.0284 0.0362 1.45 Example 13

TABLE 8 Surface-characteristics Front Back MIU MIU MIU MIU MIU MIU frontfront front back back back MIU longitudinal lateral average longitudinallateral average Average Smoothness Toilet 1P Present 0.3500~0.3800invention Example 1 0.285 0.2503 0.2677 0.2923 0.03 0.2597 0.2718 0.29Comparative 0.2773 0.2677 0.2725 0.2897 0.0305 0.2563 0.2728 2.68Example 1 Comparative 0.3003 0.292 0.2962 0.292 0.0293 0.267 0.2878 2.55Example 3 Comparative 0.314 0.2903 0.3022 0.2957 0.0293 0.2627 0.29072.26 Example 4 Comparative 0.259 0.244 0.2515 0.2523 0.0266 0.23030.2464 1.9 Example 5 Comparative 0.2597 0.232 0.2459 0.2553 0.03730.2383 0.2463 1.32 Example 6 Toilet 2P Present 0.3500~0.3800 inventionExample 2 0.4123 0.3135 0.3629 3.61 Example 3 0.389 0.3307 0.3599 3.71Comparative 0.3607 0.3513 0.356  2.52 Example 7 Comparative 0.32570.2973 0.3115 3 Example 8 Comparative 0.4063 0.372 0.3892 2.81 Example 9Comparative 0.4353 0.41 0.4227 2.26 Example 10 Comparative 0.2947 0.30030.2975 3.1 Example 11 Comparative 0.331 0.3393 0.3352 3.28 Example 12Comparative 0.335 0.3107 0.3229 1.45 Example 13

From the results above, it is appreciated that the present examples aresuperior in all of “bulk softness and thickness feeling”, “tender-touch”and “smoothness.”

INDUSTRIAL APPLICABILITY

As explained above, according to the present invention, theabove-mentioned difference in pressing depth of a sanitary tissue paperroll is set to be 2.5–3.5 mm for a two-ply or a three-ply roll, and1.5–2.5 mm for a one-ply roll. Therefore, it is possible to provide anappropriate soft feeling to a consumer who has taken the roll andstimulate his/her will to purchase this product, and thus, increasesales.

Further, since it is possible to control roll hardness of a sanitarytissue paper roll within an appropriate range, it is possible to supply,to the market, sanitary tissue paper rolls which have an appropriatetender-touch feeling.

Further, since a sanitary tissue paper roll can be provided with both anappropriate shape-maintaining ability and tender-touch feel, it issuperior not only in terms of feel but also appearance. Therefore, itwill be possible to appeal to a consumer's sense of beauty and stimulatehis/her will to purchase this product, and thus, increase sales.

Further, since it is possible to easily set a difference in pressingdepth within an appropriate range while appropriately securing aroll-shape-maintaining ability, manufacturing of a sanitary tissue paperroll according to the present invention is facilitated.

According to the present invention, a sanitary tissue paper roll will berich in thickness feeling and bulk softness while being difficult todeform, and will have a sufficient massiveness when taken in a hand,and, embosses will not easily be flattened in case embossing is applied.

According to the present invention, it is possible to provide a sanitarytissue paper which is superior and matches a human sensory evaluation,and which is highly valued in such sensory evaluation.

Further, by using three basic measurement methods and six measurementdata in combination, it is possible to quantify bulk softness,pliantness and smoothness of a toilet paper, which is one kind ofsanitary tissue paper, and manage and control a quality of the toiletpaper according to these measurement data.

1. A sanitary tissue paper for a sanitary tissue paper roll, comprising:one of a one-ply paper and a two-ply paper, wherein said one-ply paperhas characteristics such that (i) upon subjecting a sample of saidone-ply paper to a compression load of at most 50 gf/cm² betweencircular compression surfaces of steel plates, with each of the circularcompression surfaces having an area of 2 cm², and then relieving thesample of the compression load so as to allow the sample to return to anoriginal condition, a linearity of a displacement curve between thecompression load and a thickness of the sample is 0.25–0.33, and (ii)while subjecting the sample of said one-ply paper to a compression loadof 50 gf/cm² between the circular compression surfaces, a thickness ofthe sample is at least 0.14 mm, and wherein said two-ply paper hascharacteristics such that (i) upon subjecting a sample of said two-plypaper to a compression load of at most 50 gf/cm² between circularcompression surfaces of steel plates, with each of the circularcompression surfaces having an area of 2 cm², and then relieving thesample of the compression load so as to allow the sample to return to anoriginal condition, a linearity of a displacement curve between thecompression load and a thickness of the sample is 0.34–0.37, and (ii)while subjecting the sample of said two-ply paper to a compression loadof 50 gf/cm² between the circular compression surfaces, a thickness ofthe sample is at least 0.25 mm.
 2. The sanitary tissue paper accordingto claim 1, wherein said one-ply paper has characteristics such that (i)while a sample of said one-ply paper is subjected to a compression loadof 0.5 gf/cm² between the circular compression surfaces the sample has afirst thickness, and while the sample of said one-ply paper is subjectedto a compression load of 50 gf/cm² between the circular compressionsurfaces the sample has a second thickness, with a difference betweenthe first thickness and the second thickness being at least 0.20 mm, and(ii) an amount of work upon compression of the sample of said one-plypaper between the circular compression surfaces is at most 0.2000gf·cm/cm², and said two-ply paper has characteristics such that (i)while a sample of said two-ply paper is subjected to a compression loadof 0.5 gf/cm² between the circular compression surfaces the sample has afirst thickness, and while the sample of said two-ply paper is subjectedto a compression load of 50 gf/cm² between the circular compressionsurfaces the sample has a second thickness, with a difference betweenthe first thickness and the second thickness being at least 0.20 mm, and(ii) an amount of work upon compression of the sample of said two-plypaper between the circular compression surfaces is at most 0.22gf·cm/cm².
 3. The sanitary tissue paper according to claim 2, whereinsaid one-ply paper has characteristics such that when a sample of saidone-ply paper having a width of 20 cm is (i) chucked at a chuck a chuckdistance of 1 cm, then (ii) bent forward up to a maximum curvature of2.5 cm⁻¹ through pure bending by maintaining one side of the sample inthe shape of an arc, then (iii) bent back to an original position, then(iv) bent backward at a maximum curvature of −2.5 cm⁻¹, and then (v)returned to the original position, a relationship between curvature anda flexural moment exhibited by the sample demonstrates (1) said one-plypaper to have an average bending resistance in longitudinal and lateraldirections of at most 0.008 gf·cm²/cm, with the bending resistance beingexpressed as an average inclination between a curvature of 0.5–1.5 cm⁻¹,and (2) said one-ply paper to have an average flexural recoverability inthe longitudinal and lateral directions of 0.003–0.005 gf·cm/cm, withthe flexural recoverability being expressed as an average hysteresiswidth of a flexural moment between a curavature of 0.5–1.5 cm⁻¹, andsaid two-ply paper has characteristics such that when a sample of saidtwo-ply paper having a width of 20 cm is (i) chucked at a chuck a chuckdistance of 1 cm, then (ii) bent forward up to a maximum curvature of2.5 cm⁻¹ through pure bending by maintaining one side of the sample inthe shape of an arc, then (iii) bent back to an original position, then(iv) bent backward at a maximum curvature of −2.5 cm⁻¹, and then (v)returned to the original position, a relationship between curvature anda flexural moment exhibited by the sample demonstrates (1) said two-plypaper to have an average bending resistance in longitudinal and lateraldirections of at most 0.018 gf·cm²/cm, with the bending resistance beingexpressed as an average inclination between a curvature of 0.5–1.5 cm⁻¹,and (2) said two-ply paper to have an average flexural recoverability inthe longitudinal and lateral directions of 0.013–0.017 gf·cm/cm, withthe flexural recoverability being expressed as an average hysteresiswidth of a flexural moment between a curavature of 0.5–1.5 cm⁻¹.
 4. Thesanitary tissue paper according to claim 3, wherein said one-ply paperhas characteristics such that (i) an average value between an averagefriction coefficient of said one-ply paper for longitudinal and lateraldirections on a front side of said one-ply paper and an average valuebetween an average friction coefficient of said one-ply paper forlongitudinal and lateral directions on a back side of said one-ply paperis 0.260–0.280, and (ii) an average value between an average deviationof a friction coefficient for longitudinal and lateral directions on thefront side of said one-ply paper and an average deviation of a frictioncoefficient for longitudinal and lateral directions on the back side ofsaid one-ply paper is at most 0.032, with the friction coefficient forthe longitudinal and lateral directions on the front side being obtainedby (i) contacting a friction piece, made from a piano wire, having adiameter of 0.5 mm and length of 5 mm with a front side of a sample ofsaid one-ply paper along the length of the friction piece at a contactpressure of 10 gf, and then (ii) moving the friction piece at a speed of0.1 cm/second in a direction orthogonal to a length direction of thefriction piece while a tension of 20 gf/cm is applied to the sample in amoving direction of the friction piece, and with the average deviationof the friction coefficient for the longitudinal and lateral directionson the back side being obtained by (i) contacting the friction piecewith a back side of the sample of said one-ply paper along the length ofthe friction piece at a contact pressure of 10 gf, and then (ii) movingthe friction piece at a speed of 0.1 cm/second in a direction orthogonalto a length direction of the friction piece while a tension of 20 gf/cmis applied to the sample in a moving direction of the friction piece,and said two-ply paper has characteristics such that (i) an averagevalue between an average friction coefficient of said two-ply paper forlongitudinal and lateral directions on a front side of said two-plypaper and an average value between an average friction coefficient ofsaid two-ply paper for longitudinal and lateral directions on a backside of said two-ply paper is 0.350–0.380, and (ii) an average valuebetween an average deviation of a friction coefficient for longitudinaland lateral directions on the front side of said two-ply paper and anaverage deviation of a friction coefficient for longitudinal and lateraldirections on the back side of said two-ply paper is at most 0.029, withthe friction coefficient for the longitudinal and lateral directions onthe front side being obtained by (i) contacting a friction piece, madefrom a piano wire, having a diameter of 0.5 mm and length of 5 mm with afront side of a sample of said two-ply paper along the length of thefriction piece at a contact pressure of 10 gf, and then (ii) moving thefriction piece at a speed of 0.1 cm/second in a direction orthogonal toa length direction of the friction piece while a tension of 20 gf/cm isapplied to the sample in a moving direction of the friction piece, andwith the average deviation of the friction coefficient for thelongitudinal and lateral directions on the back side being obtained by(i) contacting the friction piece with a back side of the sample of saidtwo-ply paper along the length of the friction piece at a contactpressure of 10 gf, and then (ii) moving the friction piece at a speed of0.1 cm/second in a direction orthogonal to a length direction of thefriction piece while a tension of 20 gf/cm is applied to the sample in amoving direction of the friction piece.
 5. The sanitary tissue paperaccording to claim 4, wherein said one-ply paper and said two-ply papereach have (i) grammage of 15–25 g/m², (ii) a thickness of 120–180 μm,(iii) a longitudinal/lateral ratio of tension of 2.0–3.0, (iv) anelongation rate in a longitudinal direction of 20–35%, (v) alongitudinal tensile strength of 110–115 N/m, and (vi) 30–50 crepes percm.
 6. A sanitary tissue paper roll comprising a roll of the two-plypaper according to claim 4, wherein said roll, and a difference indepths resulting from pressing at the respective pressing pressures iscontinuously measured nine times, a difference between a maximum and aminimum of these nine differences in depth is within a range of 0.5–1.0mm.
 7. The sanitary tissue paper roll according to claim 6, wherein saidroll of the two-ply paper has characteristics such that when adifference in depths resulting from pressing at the respective pressuresis continuously measured nine times, each of these nine differences indepth is within the range of 2.5–3.5 mm, and a difference between amaximum and a minimum of these nine differences in depth is within arange of 0.5–1.0 mm.
 8. A sanitary tissue paper roll comprising a rollof the one-ply paper according to claim 4, wherein said roll of theone-ply paper has characteristics such that when said roll is on ahorizontal surface, with a central axis of said roll horizontallyoriented, and a circular plate indenter having an area of 2 cm² isvertically pressed, at least at respective pressing pressures of 0.5gf/cm² and 50 gf/cm², against a central portion of an upper surface ofan outer periphery of said roll, a difference in depths resulting frompressing at the respective pressing pressures is within a range of1.5–2.5 mm.
 9. A sanitary tissue paper roll comprising a roll of thesanitary tissue paper according to claim 4, wherein said roll of thesanitary tissue paper has characteristics such that when said roll is ona horizontal surface, with a central axis of said roll horizontallyoriented, and a circular plate indenter having an area of 2 cm² isvertically pressed, at least at respective pressing pressures of 0.5gf/cm² and 50 gf/cm², against a central portion of an upper surface ofan outer periphery of with each of said sheets having a grammage of15–25 g/m², a density of 0.10–0.15 g/cm³, and a thickness of 20–170 μm.10. A sanitary tissue paper roll comprising a roll of the sanitarytissue paper according to claim 4, wherein an elongation rate saidsanitary tissue paper in a longitudinal direction of said sanitarytissue paper is 20–35%.
 11. A sanitary tissue paper roll comprising aroll of the sanitary tissue paper according to claim 4, wherein saidroll is formed by winding said sanitary tissue paper such that a rollcompressibility of said roll is 0.68–0.74 m/cm², with said rollcompressibility being defined as a value obtained by dividing a lengthof said roll by a cross section of said roll.
 12. The sanitary tissuepaper roll according to claim 11, wherein said roll of the sanitarytissue paper comprises wound sheets of said sanitary tissue paper, withsaid sanitary tissue paper having characteristics such that a dry-statetensile strength, which is measured according to atensile-characteristic testing method defined by JISP8113, for each ofsaid sheets is at least 40 N/m in a width direction, and is 1–4 folds ofthe width direction in a longitudinal direction.
 13. The sanitary tissuepaper roll according to claim 11, wherein a number of crepes per cm ofsaid sanitary tissue paper is 25–45 per cm, and an elongation rate ofsaid sanitary tissue paper in a longitudinal direction is 15–25%. 14.The sanitary tissue paper roll according to claim 11, wherein said rollof the sanitary tissue paper comprises wound sheets of said sanitarytissue paper, said roll of the two-ply paper has characteristics suchthat when said roll is on a horizontal surface, with a central axis ofsaid roll horizontally oriented, and a circular plate indenter having anarea of 2 cm² is vertically pressed, at least at respective pressingpressures of 0.5 gf/cm² and 50 gf/cm², against a central portion of anupper surface of an outer periphery of said roll, a difference in depthsresulting from pressing at the respective pressing pressures is within arange of 2.5–3.5 mm.
 15. The sanitary tissue paper roll according toclaim 11, wherein said sanitary tissue paper comprises a paper mademainly of Nadelholz bleached kraft pulp and Laubholz bleached kraft pulpand having a weight proportion of Nadelholz bleached kraft pulp toLaubholz bleached kraft pulp of 10:90–70:30.
 16. The sanitary tissuepaper roll according to claim 11, wherein said sanitary tissue paper isembossed prior to winding said sanitary tissue paper to form said roll.17. The sanitary tissue paper roll according to claim 11, wherein whensaid roll is formed by winding said one-ply paper, a roll length is58–65 m, and when said roll is formed by winding said two-ply paper, aroll length is 29–33 m.
 18. The sanitary tissue paper roll according toclaim 11, wherein said roll is formed made by winding said sanitarytissue paper around a core having an outer diameter of 30–40 mm.
 19. Asanitary tissue paper for a sanitary tissue paper roll, comprising: oneof a one-ply paper and a two-ply paper, wherein said one-ply paper hascharacteristics such that when a sample of said one-ply paper having awidth of 20 cm is (i) chucked at a chuck a chuck distance of 1 cm, then(ii) bent forward up to a maximum curvature of 2.5 cm⁻¹ through purebending by maintaining one side of the sample in the shape of an arc,then (iii) bent back to an original position, then (iv) bent backward ata maximum curvature of −2.5 cm⁻¹, and then (v) returned to the originalposition, a relationship between curvature and a flexural momentexhibited by the sample demonstrates (1) said one-ply paper to have anaverage bending resistance in longitudinal and lateral directions of atmost 0.008 gf·cm²/cm, with the bending resistance being expressed as anaverage inclination between a curvature of 0.5–1.5 cm⁻¹, and (2) saidone-ply paper to have an average flexural recoverability in thelongitudinal and lateral directions of 0.003–0.005 gf·cm/cm, with theflexural recoverability being expressed as an average hysteresis widthof a flexural moment between a curavature of 0.5–1.5 cm⁻¹, and whereinsaid two-ply paper has characteristics such that when a sample of saidtwo-ply paper having a width of 20 cm is (i) chucked at a chuck a chuckdistance of 1 cm, then (ii) bent forward up to a maximum curvature of2.5 cm⁻¹ through pure bending by maintaining one side of the sample inthe shape of an arc, then (iii) bent back to an original position, then(iv) bent backward at a maximum curvature of −2.5 cm⁻¹, and then (v)returned to the original position, a relationship between curvature anda flexural moment exhibited by the sample demonstrates (1) said two-plypaper to have an average bending resistance in longitudinal and lateraldirections of at most 0.018 gf·cm²/cm, with the bending resistance beingexpressed as an average inclination between a curvature of 0.5–1.5 cm⁻¹,and (2) said two-ply paper to have an average flexural recoverability inthe longitudinal and lateral directions of 0.013–0.017 gf·cm/cm, withthe flexural recoverability being expressed as an average hysteresiswidth of a flexural moment between a curavature of 0.5–1.5 cm⁻¹.
 20. Asanitary tissue paper for a sanitary tissue paper roll, comprising: oneof a one-ply paper and a two-ply paper, wherein said one-ply paper hascharacteristics such that (i) an average value between an averagefriction coefficient of said one-ply paper for longitudinal and lateraldirections on a front side of said one-ply paper and an average valuebetween an average friction coefficient of said one-ply paper forlongitudinal and lateral directions on a back side of said one-ply paperis 0.260–0.280, and (ii) an average value between an average deviationof a friction coefficient for longitudinal and lateral directions on thefront side of said one-ply paper and an average deviation of a frictioncoefficient for longitudinal and lateral directions on the back side ofsaid one-ply paper is at most 0.032, with the friction coefficient forthe longitudinal and lateral directions on the front side being obtainedby (i) contacting a friction piece, made from a piano wire, having adiameter of 0.5 mm and length of 5 mm with a front side of a sample ofsaid one-ply paper along the length of the friction piece at a contactpressure of 10 gf, and then (ii) moving the friction piece at a speed of0.1 cm/second in a direction orthogonal to a length direction of thefriction piece while a tension of 20 gf/cm is applied to the sample in amoving direction of the friction piece, and with the average deviationof the friction coefficient for the longitudinal and lateral directionson the back side being obtained by (i) contacting the friction piecewith a back side of the sample of said one-ply paper along the length ofthe friction piece at a contact pressure of 10 gf, and then (ii) movingthe friction piece at a speed of 0.1 cm/second in a direction orthogonalto a length direction of the friction piece while a tension of 20 gf/cmis applied to the sample in a moving direction of the friction piece,and wherein said two-ply paper has characteristics such that (i) anaverage value between an average friction coefficient of said two-plypaper for longitudinal and lateral directions on a front side of saidtwo-ply paper and an average value between an average frictioncoefficient of said two-ply paper for longitudinal and lateraldirections on a back side of said two-ply paper is 0.350–0.380, and (ii)an average value between an average deviation of a friction coefficientfor longitudinal and lateral directions on the front side of saidtwo-ply paper and an average deviation of a friction coefficient forlongitudinal and lateral directions on the back side of said two-plypaper is at most 0.029, with the friction coefficient for thelongitudinal and lateral directions on the front side being obtained by(i) contacting a friction piece, made from a piano wire, having adiameter of 0.5 mm and length of 5 mm with a front side of a sample ofsaid two-ply paper along the length of the friction piece at a contactpressure of 10 gf, and then (ii) moving the friction piece at a speed of0.1 cm/second in a direction orthogonal to a length direction of thefriction piece while a tension of 20 gf/cm is applied to the sample in amoving direction of the friction piece, and with the average deviationof the friction coefficient for the longitudinal and lateral directionson the back side being obtained by (i) contacting the friction piecewith a back side of the sample of said two-ply paper along the length ofthe friction piece at a contact pressure of 10 gf, and then (ii) movingthe friction piece at a speed of 0.1 cm/second in a direction orthogonalto a length direction of the friction piece while a tension of 20 gf/cmis applied to the sample in a moving direction of the friction piece.